Oximes acyloximes

In contrast, oxime ethers and esters are usually stable in solution but the E/Z isomerization can be induced by acids " or by irradiation ". Recently, Narasaka and colleagues"" "" studied the equilibration-isomerization of (E)-O-acyl oximes 239 in the presence of an acid in a nucleophilic solvent (equation 71). Isomerization probably proceeds via protonation of the oxime nitrogen followed by addition-elimination of a nucleophilic solvent until the equilibrium of E and Z isomers is achieved. The isomerization of the more labile 0-acyloximes occurs either by an Sjv2 substitution at the oxime nitrogen with acids and/or by acyl exchange through the formation of a mixed anhydride and the free oxime. 

Copolymers of 2,3-butanedione-2-< -methacryloyl-oxime with MMA [poly (BOMA-co-MMA)], containing different amounts (7-30 mol%) of side-chain O-acyloxime moieties, have also been used [75] as macro-initiators for the photochemical grafting of styrene and acrylamide in benzene and dioxane solution, respectively,... 

The second approach, by Menichincheri and her associates, used the oxime 2.2.5, prepared from baccatin III, as their key intermediate (45). Acylation with protected side chain gave an unstable acyloxime which... 

Br0nsted coefficients for esterolytic reactivity of anionic nucleophiles in micelles are quite small, so that oximates and hydroxamates are much more reactive than hydroxide ion at a given pH in the weakly basic region. Thus the surfactant (64) is claimed to be the most powerful among functional micelleforming species in promoting the transacylation of p-nitrophenyl acetate and hexanoate. The acyloxime is hydrolysed quite slowly at pH 8, so that catalytic turnover is feeble.Oximate (65) catalyses the hydrolysis of phosphate ester... 

---